refactor: hide mutable primitive codec array

PRIMITIVE_CODECS is an array, so final only prevents reassigning the field; callers that can reach a public field can still mutate its contents.

The array is only used by codec registry internals, so keep it package-private instead of exposing mutable static state. This avoids MutablePublicArray-style warnings without changing registry behavior.

Author: dkropachev

core/src/main/java/com/datastax/oss/driver/internal/core/type/codec/registry/CodecRegistryConstants.java

@@ -32,7 +32,7 @@ public class CodecRegistryConstants {
    * DefaultCodecRegistry#DefaultCodecRegistry(String, int, BiFunction, int, BiConsumer,
    * TypeCodec[])} but only customize the caching options.
    */
-  public static final TypeCodec<?>[] PRIMITIVE_CODECS =
+  static final TypeCodec<?>[] PRIMITIVE_CODECS =
       new TypeCodec<?>[] {
         // Must be declared before AsciiCodec so it gets chosen when CQL type not available
         TypeCodecs.TEXT,